1. Field of the Invention
The invention is based on a hydraulic control device for an injector of a fuel injection system in motor vehicles.
2. Description of the Prior Art
One hydraulic control device known from German Patent Disclosure DE 196 24 001 A1 comprises a piezoelectric actuator and a multi-position valve, controlled by the actuator, with a valve member guided displaceably in a valve bore. The multiposition valve is embodied as a conventional seat valve and controls a pressure fluid connection between a pressure fluid conduit, which carries fuel under high pressure, and a return line. In the non-triggered state of the actuator, the valve member is lifted from the valve seat and thus opens the aforementioned pressure fluid connection. As a result, the pressure level in an injection nozzle, also coupled to the pressure fluid conduit that carries high pressure, drops. Once the pressure drops below a mechanically specified opening pressure, a pressure-controlled closing element of the injection nozzle uncovers injection openings. Through these injection openings, fuel reaches a combustion chamber of an internal combustion engine. With the closure of the valve seat by an electrical triggering of the actuator, the injection event is terminated.
The pressure drop at the valve seat is in the same direction as the stroke motion of the valve member, so that the multi-position valve forms an outward opening or so-called A-valve. Outward-opening valves have fluid disadvantages, since the closing motion takes place counter to high pressure, and hence the actuator must be embodied as suitably powerful and voluminous. Furthermore, outward-opening valves are more expensive to produce.
The hydraulic control device of the invention has the advantage of being embodied as an inward-opening I-valve. In inward-opening valves, the pressure drop at the valve seat is oriented counter to the direction of motion of the valve member. As a result, upon opening of the multi-position valve, the stroke motion of the valve member is reinforced by an additional hydraulic force, so that actuators with lesser actuating forces suffice to control the valve. Such actuators are correspondingly smaller in size and more compact and require less electrical power. The load on the actuators thus drops, so that they function more robustly and reliably.